WSJ's Douglas Macmillan joins digits to explain how Foursquare can now track users' GPS coordinates even when the app is closed, as long as their phone is powered on. Photo: iStock/hocus-focus.

This transcript has been automatically generated and may not be 100% accurate.

... I ... for for a spying on you even when ... the phone is off will commit Digits I'm Simon Constable ... and isn't done MacMillan from the will Street gentle to tell us more about this book thanks for being an things happening ... so for twelve which it was the last we checked in places may be discount songs off ... the spying on you ... full time mom I was right ... well Eddie overstating it a bit so they update and the little that ... content they figure if you're dedicated users of Foursquare I knew ... you update the app today or your new user new stocks today what you are doing is giving them permission ... to track your location and GPS ordnance wherever you go even if the app ... is close and the pointed this is they say that they want to ... gather smarter recommendations so that instead of just learned about you buy what you say you lie ... there to learn about you by where you go in the things that you actually do the bars he gets you in the conscience that unit and restaurants where we're still in passing to some people out if they don't even remember it depending on how well a new brand sales ... that any sum this all this is a call today you can you can send it's what what you would call an opt out feature ... aam which is done is in contrast to what most companies are doing these days when it comes to matters of privacy ... is off and meaning you have to get the users the choice to express league information ... on their head and actions by regulators ... the FTC ... aam has ... this asset at a summit with Facebook saying that ... Facebook users Facebook ... on how to make its price changes his privacy ops and when you have to go ... and agree to them expressly ... support for sticking to rescue the same ... we want to bring as many of our users as the can ... onto this featured on the stool sing gather more data the more willing to risk dying of some of them being called weirded out but it's not just talking about the with that of gamble getting sick of this By thing with little about the NSA when we we we thought about other social media ... some locations doing strange things to people I mean that that was the site off ... but now ... I think there's a long time where companies aam benefited from the fact that you just didn't care about privacy but now we are now yes we are living in an era of aam people caring about the stock is all the sudden on people's minds and the starting to think ... kind of harder about what kind of data they are putting on a mobile devices ... so when it comes to us with this could be a trade off right between you giving up something when you get the time it is his fourth wicket of the overall fee you enough fall enough people yet our means be seen on nitrogen it to download the app and tried out I've given it a whirl today and we'll see if they live up to this claim that were building some of the smartest recommendation ... Engine out there they can ... aam deliver me to the best restaurant and do that consistently in new towns come to discover new things ... perhaps that is worth getting up so my data and in a trust them enough to handle a data properly that might be a tradeoff that some users are on a ... multiple weasel say well we thank you very much what mom a lot of the Wall Street John all I'm Simon Constable Matt said